Conformism and cooperation in a local interaction model

We analyze a local interaction model where agents play a bilateral prisoner’s dilemma game with their neighbors. Agents learn about behavior through payoff-biased imitation of their interaction neighbors (and possibly some agents beyond this set). We find that the Eshel et al. (Am Econ Rev 88:157–179, 1998) result that polymorphic states are stochastically stable in such a setting is not robust. In particular, whenever agents use information also of some agents beyond their interaction neighbors, the unique stable outcome is one where everyone chooses defection. Introducing a sufficiently strong conformist bias into the imitation process, we find that full cooperation always emerges. Conformism is thus identified as a new mechanism that can stabilize cooperation.

Nonparametric learning rules from bandit experiments: The eyes have it!

How do people learn? We assess, in a model-free manner, subjectsʼ belief dynamics in a two-armed bandit learning experiment. A novel feature of our approach is to supplement the choice and reward data with subjectsʼ eye movements during the experiment to pin down estimates of subjectsʼ beliefs. Estimates show that subjects are more reluctant to “update down” following unsuccessful choices, than “update up” following successful choices. The profits from following the estimated learning and decision rules are smaller (by about 25% of average earnings by subjects in this experiment) than what would be obtained from a fully-rational Bayesian learning model, but comparable to the profits from alternative non-Bayesian learning models, including reinforcement learning and a simple “win-stay” choice heuristic.     

Imitation and the role of information in overcoming coordination failures

We consider minimum-effort games played in an arbitrary network. For a family of imitation behavioral rules, including Imitate the Best and the Proportional Imitation Rule, we show that inefficient conventions arise independently of the interaction structure, if information is limited to the interaction neighborhoods. In the presence of information spillovers, we provide a condition on the network structure that guarantees the emergence of efficient conventions. In contrast, if this condition is violated we will observe inefficient conventions, even in the presence of information spillovers.     

Hierarchical thinking and learning in rank order contests

We analyze a class of coordination games in which the Kth player to submit an entry wins a contest. These games have an infinite number of symmetric equilibria and the set of equilibria does not change with K. We run experiments with 15 participants and with K=3, 7, and 11. Our experiments show that the value of K affects initial submissions and convergence to equilibrium. When K is small relative to the number of participants, our experiments show that repeated play converges to or near zero. When K is large, an equilibrium is often not reached as a result of repeated play. We seek explanations to these patterns in hierarchical thinking and direction learning.      

Information and learning in oligopoly: An experiment

This paper presents an experiment on learning in repeated games, which complements the analysis of playersʼ actual choices with data on the information acquisition process they follow. Subjects play a repeated Cournot oligopoly, with limited a priori information. The econometrics hinges on a model built upon Experience Weighted Attraction learning, and the simultaneous analysis of data on the information gathered and on actions taken by the subjects. Results suggest that learning is a composite process, in which different components coexist. Adaptive learning emerges as the leading element, but when subjects look at the strategies individually adopted by their competitors they tend to imitate the most successful behavior, which makes markets more competitive. Reinforcement learning also plays a role, as subjects favor strategies that have yielded higher profits in the past.     

Information feedback and contest structure in rent-seeking games

We investigate the effects of information feedback in rent-seeking games with two different contest structures. In the share contest a contestant receives a share of the rent equal to her share of rent-seeking expenditures, while in the lottery contest a contestant wins the entire rent with probability equal to her share of rent-seeking expenditures. In share contests average expenditures converge to equilibrium levels when subjects only get feedback about own earnings, and additional feedback about rivals' choices and earnings raises average expenditures. In lottery contests information feedback has an opposite, and even stronger, effect: when subjects only get feedback on own earnings we observe high levels of rent dissipation, usually exceeding the value of the rent, and additional feedback about rivals' choices and earnings has a significant moderating influence on expenditures. In a follow-up treatment we make information feedback endogenous by allowing contestants in a lottery contest to make public or private expenditures. Subjects make the vast majority of expenditures privately and overall excess expenditures are similar to the lottery contest with own feedback.     

Economic inequality and burden-sharing in the provision of local environmental quality

A large, but inconclusive, literature addresses how economic heterogeneity affects the use of local resources and local environmental quality. One line of thought, which derives from Nash equilibrium provision of public goods, suggests that in contexts in which individual actions degrade local environmental quality, wealthier people in a community will tend to do more to protect environmental quality. In this paper we report on experiments performed in rural Colombia that were designed to explore the role that economic inequality plays in the ‘provision’ of local environmental quality. Subjects were asked to decide how much time to devote to collecting firewood from a local forest, which degrades local water quality, and how much to unrelated pursuits. Economic heterogeneity was introduced by varying the private returns to these alternative pursuits. Consistent with the Nash equilibrium prediction, we found that the players with more valuable alternative options put less pressure on local water quality. However, the subjects with less valuable alternative options showed significantly more restraint relative to their pure Nash strategies. Furthermore, they were willing to bear significantly greater opportunity costs to move their groups to outcomes that yielded higher average payoffs and better water quality than the Nash equilibrium outcome.     

An experiment on learning with limited information: nonconvergence, experimentation cascades, and the advantage of being slow

We present the results of an experiment on learning in a continuous-time low-information setting. For a dominance solvable version of a Cournot oligopoly with differentiated products, we find little evidence of convergence to the Nash equilibrium. In an asynchronous setting, characterized by players updating their strategies at different frequencies, play tends toward the Stackelberg outcome which favors the slower player. Convergence is significantly more robust for a “serial cost sharing” game, which satisfies a stronger solution concept of overwhelmed solvability. As the number of players grows, this improved convergence tends to diminish, seemingly driven by frequent and highly structured experimentation by players leading to a cascading effect in which experimentation by one player induces experimentation by others. These results have implications both for traditional oligopoly competition and for a wide variety of strategic situations arising on the Internet.     

Entry in contests with incomplete information: Theory and experiments

This paper studies entry decisions in contests with private values. Potential contestants observe their value and the common opportunity cost of entry, and make entry decisions simultaneously. Theory predicts that whether or not contestants are informed of the number of entrants prior to choosing their expenditures has no effect on entry or aggregate expenditures. We test these assertions in our experiments. We find substantial over-entry in both information structures. However, entry is higher when contestants are informed. Since expenditures do not, on average, differ across information structures, aggregate expenditure is also higher when contestants are informed. Contestants earn on average less than the opportunity cost of entry.     

Overbidding and overspreading in rent-seeking experiments: Cost structure and prize allocation rules

We study experimentally the effects of cost structure and prize allocation rules on the performance of rent-seeking contests. Most previous studies use a lottery prize rule and linear cost, and find both overbidding relative to the Nash equilibrium prediction and significant variation of efforts, which we term ‘overspreading.’ We investigate the effects of allocating the prize by a lottery versus sharing it proportionally, and of convex versus linear costs of effort, while holding fixed the Nash equilibrium prediction for effort. We find the share rule results in average effort closer to the Nash prediction, and lower variation of effort. Combining the share rule with a convex cost function further enhances these results. We can explain a significant amount of non-equilibrium behavior by features of the experimental design. These results contribute towards design guidelines for contests based on behavioral principles that take into account implementation features of a contest.     

Coordination and learning in games with strategic substitutes and complements

This paper experimentally compares the impact of the presence of strategic substitutes (GSS) and complements (GSC) on players’ ability to successfully play equilibrium strategies. By exploiting a simple property of the ordering on strategy spaces, our design allows us to isolate these effects by avoiding other confounding factors that are present in more complex settings, such as market games. We find that the presence of strategic complementarities significantly improves the rate of Nash play, but that this effect is driven mainly by early rounds of play. This suggests that GSS may be more difficult to learn initially, but that given sufficient time, the theoretically supported globally stable equilibrium offers a good prediction in both settings. We also show that increasing the degree of substitutability or complementarity does not significantly improve the rate of Nash play in either setting, which builds on the findings of previous studies.     

Behavior in one-shot traveler’s dilemma games: model and experiments with advice

We report results of one-shot traveler’s dilemma game experiments to test the predictions of a model of introspection. The model describes a noisy out-of-equilibrium process by which players reach a decision of what to do in one-shot games. To test the robustness of the model and to compare it to other models of introspection without noise, we introduce non-binding advice. Advice has the effect of coordinating all players’ beliefs onto a common strategy. Experimentally, advice is implemented by asking subjects who participated in a repeated traveler’s dilemma game to recommend an action to subjects playing one-shot games with identical parameters. In contrast to observations, models based on best-response dynamics would predict lower claims than the advised. We show that our model’s predictions with and without advice are consistent with the data.      

Equilibria in systems of social interactions

In this paper, we establish existence and uniqueness results for equilibria in systems with an infinite number of agents and with local and global social interactions. We also examine the structure of the equilibrium distribution and derive a “Markov”property for the equilibrium distribution of a class of spatially homogeneous systems.     

Diversity,effort, and cooperation in team-based learning

Student and team performance in 17 sections of an introductory microeco-nomic theory course taught using team-based learning are analyzed to determine what measurable characteristics of teams influence team and individual outcomes. Results suggest that team performance is positively influenced by the grade point average of the top individual on the team as well as the percentage of females on the team. While the level of cooperation within a team does not significantly influence team outcomes, it positively influences individual performance by females while having no statistically significant influence on male performance. Individual success also is positively and significantly influenced by gender diversity and individual effort in team activities, as measured by peer evaluations. These results are robust to a variety of measures of gender diversity.     

Factors substitutability,heterogeneity and endogenous fluctuations in a finance constrained economy

Summary.   This paper examines the local properties of perfect foresight equilibrium of a finance constrained economy featuring two classes of infinitely-lived agents with heterogeneous general preferences. It is primarily concerned with the conceivability of endogenous fluctuations for large plausible capital-labor elasticities of substitution. It is notably shown that heterogeneity in preferences allows Hopf cycles to be entirely consistent with a wide range of elasticities of substitution including the unitary one (Cobb-Douglas specifications). Received: April 23, 1999; revised version: January 24, 2000     

Endogenous transfers in the Prisoner's Dilemma game: An experimental test of cooperation and coordination

We test a two-stage compensation mechanism for promoting cooperation in Prisoner's Dilemma games. Players first simultaneously choose binding non-negative amounts to pay their counterparts for cooperating, and then play the induced game knowing these amounts. In our games, all payment pairs consistent with mutual cooperation in subgame-perfect equilibrium transform these games into coordination games, with both mutual cooperation and mutual defection as Nash equilibria in the second stage. When endogenous transfer payments are not permitted, cooperation is much less likely. Mutual cooperation is most likely when the (sufficient) payments are identical, and it is also substantially more likely with payment pairs that bring the mutual-cooperation payoffs closer together. Both the Fehr–Schmidt and Charness–Rabin models predict that transfers that make final payoffs closer are preferred; however, they do not explain why equal transfers are particularly effective. Transfers are also effective in sustaining cooperation even when they are imposed and not chosen.     

Market crashes,speculation and learning in financial markets

A natural conjecture is that if agents’ beliefs are almost correct then equilibrium prices should be close to rational expectations prices. Sandroni (J Econ Theory 82:1–18, 1998) gives a counterexample in an economy with sunspots and complete markets. We extend Sandroni’s result by showing that the conjecture is generically true for economies with complete markets. We consider a standard General Equilibrium model with large but finite horizon and complete markets. We show that, for almost every such economy, if conditional beliefs eventually become correct along a path of events then equilibrium prices of assets traded along this path converge to rational expectations equilibria in the sup-norm. Moreover, we establish that, generically, there exist along any such path local diffeomorphisms between individual beliefs and equilibrium prices. I would like to thank C. Ewerhart and A. Kirman for their comments, as well as the seminar participants at the University of Minho, the General Equilibrium Workshop 2005 in Zurich, and the 15th Asian General Equilibrium Conference 2007 in Singapore. An anonymous referee also provided very valuable comments.     

中国地级城市行政环境与政府门户网站绩效关系的实证研究

本文以行政生态学为理论根据,以我国地级城市为研究样本,通过收集现存统计数据的方法对行政环境与政府门户网站绩效二者关系进行实证检验.研究结果表明,我国地级城市行政环境对政府门户网站绩效有显著影响.本研究从行政生态学角度探索电子政务发展的潜在规则,研究结果为营造有利于我国电子政务可持续发展的生态环境提供指导.